Disclosed embodiments concern a composition and/or combination, and a method of administering the same as a feed, or to supplement the feed of, aquatic animals, particularly for aquaculture. Disclosed composition and/or combination embodiments may comprise glucan, silica, mineral clay, mannans, yucca, quillaja, a probiotic, and/or an adhesive agent. The adhesive agent may be selected particularly to facilitate administration to aquatic species. In certain embodiments the adhesive agent comprises an oil, such as soy oil, or a syrup, such as molasses, or combinations thereof. In some embodiments the composition and/or combination may further comprise polyphenol, an antimicrobial, and/or a vaccine. Also disclosed is a method for promoting growth and/or immune function in aquatic animals.